Feltia subgothica Haworth Lepidoptera Noctuidae

Natural History

Distribution. The name "dingy cutworm" is applied to at least two, and possibly four, species in

North America. Possibly the most important is F. jaculifera, also known as F. ducens Walker. Second in importance usually is F. subgothica, but F. tricosa Lint-ner and F. herilis (Grote) are very similar in appearance and biology. The literature on these species is terribly confused, and they usually are treated as a complex of co-occurring species (Chapman and Lienk, 1981). The distribution of this cutworm complex is most of the United States and southern Canada. They are absent only from southern Florida and from California and adjacent desert areas (Rings et al., 1975). They are most damaging in the midwestern and eastern states, and eastern Canada.

Host Plants. Dingy cutworm is commonly known as a corn pest, but also feeds on such vegetables as bean, cabbage, celery, cucumber, lettuce, onion, pea, squash, sweet potato, and tomato. Among other crops injured are alfalfa, blue grass, clover, flax, horseradish, raspberry, sweetclover, tobacco, and wheat. A wide variety of weeds are suitable food for dingy cutworm, including aster, Aster ericoides; chickweed, Stellaria sp.; goldenrod, Solidago sp.; mullein, Verbascum sp.; plantain, Plantago sp.; and yellow dock, Rumex crispus.

Natural Enemies. Collection of larvae in spring from the central Great Plains has shown that natural enemies may account for 28% mortality, with most attributable to parasitoids (Walkden, 1950). Among the wasps parasitizing dingy cutworm are Aleiodes aci-culatus Cresson, Chelonus sericeus (Say), Apanteles griffini Viereck, Microplitis feltiae Muesbeck, Meteorus leviventris (Wesmael), Spilichneumon superbus (Provan-cher) (all Hymenoptera: Braconidae), and Copidosoma bakeri (Howard) (Hymenoptera: Encyrtidae). Flies known to parasitize dingy cutworms include Euphoro-cera claripennis (Macquart), Gonia frontosa Say, G. fusci-collis Tothill, Triachora omissa (Aldrich), and Winthemia quadripustulata (Fabricius). A nematode, Hexamermis arvalis (Nematoda: Mermithidae) infects young dingy cutworms in the autumn and emerges in the spring, killing the larvae (Puttler and Thewke 1971). Diseases known to affect dingy cutworm include the fungi Beauveria sp. and Metarhizium anisopliae and an unspecified virus (Crumb, 1929).

Life Cycle and Description. There is a single generation of dingy cutworm annually. Moth flight occurs in July-September, followed immediately by oviposi-tion. Larvae hatch and become partly grown before the onset of winter. Dingy cutworm overwinters in the larval stage, with larval development normally completed in March-May. The larvae remain quiescent in the soil until August, when pupation occurs, followed immediately by emergence of the adults. Fel-tia jaculifera usually lags behind the other species in appearing as an adult. In New York, F. jaculifera nor mally first occurs in early August, whereas the other species comprising the dingy cutworm complex first appear in mid-July (Chapman and Lienk, 1981).

  1. The eggs reportedly are deposited on vegetation and on the soil surface. However, Balduf (1931) described deposition of eggs into flower heads of sunflowers. The eggs are oval, whitish to light brown, and the surface is marked by about 36 (F. jaculifera) or 56 (F. subgothica) narrow ridges. They measure about 0.60-0.65 mm long, 0.5 mm wide, and 0.36-0.38 mm in height. Duration of the egg stage is 5-21 days, depending on weather conditions, but normally 6-11 days. Based on dissections, females appear to be capable of producing about 800 eggs (range 500-1220 eggs). However, when Stanley (1936) captured moths feeding at flowers and confined them, he observed egg production of only about 100 eggs per female.
  2. Larvae display 6-7 instars, with 6 being normal. Head capsule widths are 0.30, 0.4-0.5, 0.550.80, 0.80-1.25,1.30-1.90,1.90-2.50, and 2.30-2.80 mm for instars 1-7, respectively. Duration of the instars is normally 3-12,4-12,4-12,5-17,8-119,15-160, and 18222 days, respectively. Total larval development time is 250-350 days. Body size increases from about 3 mm to 22-32 mm over the course of development. The body color is grayish brown. An interrupted blackish stripe is found dorsolaterally, bounding a broad lighter dorsal band. The head is brownish gray, and marked with darker regions. The larvae of dingy cutworm are extremely hardy, able to tolerate long periods without food. They rarely display a tendency to climb, preferring to feed along the soil surface. Larvae

Dingy cutworm larva.

Dingy cutworm larva.

are normally considered to be foliage feeders, and in the early spring this is certainly the case. However, Balduf (1931) described pollen consumption by first instar larvae, and Duffus et al. (1983) indicated that larvae may feed until the fourth instar on sunflower heads. (See color figure 50.)

  1. Larvae prepare a cell in the upper 1-2 cm of the soil, and pupate within. The pupa is brown, and measures about 18 mm long and 6 mm wide. Duration of the pupal stage is 12-35 days.
  2. The moths are brownish and measure 3542 mm in wingspan. The front wings are grayish-brown marked with darker brown and a hint of purple. The hind wings may be whitish basally and brown distally, or uniformly brown. The thorax and abdomen are gray to brown. Adults live for 5-10 days. Moths reportedly are affected by weather, with significant effects on reproductive success. Specifically, F. jaculifera is reported to be favored by dry weather during autumn, especially in October, because moths are most likely to fly and oviposit. In the case of F. sub-gothica, dry weather during September is favorable (Stanley, 1936). (See color figure 237.)

Sex pheromones have been described for F. jaculifera (Byers and Struble 1990). It appears, based on pheromone studies, that there is a genetic substructur-ing of the nominal species known as F. jaculifera. The 'pheromonal strains' respond to at least four slightly different pheromones (Byers et al., 1990), but the genetic differences among strains are, as yet, too small to be considered different species (Gooding et al., 1992).

A detailed description of dingy cutworm is provided by Crumb (1929), and it was included in keys by Whelan (1935), Crumb (1956), Rings (1977b), Capi-nera (1986), and in a key to armyworms and cutworms in Appendix A. The moths were included in keys by Rings (1977a), Oliver and Chapin (1981), and Capinera and Schaefer (1983). Developmental data were provided by Walkden (1950). Chapman and Lienk (1981) made valuable observations on the species complex comprising dingy cutworm. A bibliography on dingy cutworm was published by Rings et al., 1975a.

Damage

Larvae damage young plants in the spring, usually by cutting the seedlings off at the soil surface. In a survey of midwestern corn fields conducted between 1979 and 1981, dingy cutworm was the second most abundant cutworm encountered, following only black cutworm, Agrotis ipsilon (Hufnagel) in abundance (Story et al., 1984). On occasion, larvae have been observed

Adult dingy cutworm.

to ascend plants, including trees, to feed on buds and young foliage.

Management

  1. The adult populations may be monitored with light or pheromone, but because plant damage does not occur for several months after adult activity, larval monitoring is needed. Duffus et al. (1983) compared five types of larval sampling protocols and recommended sack trapping—the collection of larvae from beneath squares of plastic or burlap.
  2. Cutworms can be controlled by application of persistent insecticides to soil or plants, or by application of baits such as bran that have been treated with insecticide. Bacillus thuringiensis is not usually recommended for control of this insect.

Cultural Practices. If seedlings are to be transplanted into the home garden, larger plants are preferred, because they are less likely to be irreparably damaged by cutworms. Transplanted plants can be protected if surrounded by a barrier such as a can or waxed-paper container with the bottom removed. Aluminum foil wrapped around the base of the seedling also deters cutting by larvae.

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